This invention relates generally to fire extinguishing sprinkler heads, and more particularly to upright sprinkler heads disposed above a water or other fire extinguishing fluid supply pipe.
Fire extinguishing sprinkler heads come in three general types: upright pendant, and sidewall. Of particular interest to the present application are the upright and pendant types. Pendant sprinkler heads are sprinkler heads that hang below a fire extinguishing fluid supply pipe, such as a water pipe. Examples of two different positionings of prior art pendant sprinkler heads are shown in FIG. 1. As one example, a sprinkler head 10 depends downwardly directly from a water supply pipe 12. As another example, sprinkler head 10A also depends downwardly from water supply pipe 12, but is attached to a downward extension pipe 14. Both sprinkler heads are of the pendant type. When a fire is detected, the water flows through sprinkler head 10 and downwardly over an area to be sprinkled. As the water exits from the sprinkler head, it is typically dispersed by a deflector 16 that distributes the relatively compact and concentrated flow of water coming from the supply pipes.
An upright sprinkler differs from a pendant sprinkler in that it is disposed above the water supply pipe. When an upright sprinkler is activated, the water flows upward through the sprinkler and exits a central orifice in the sprinkler head while traveling upward. Gravity, in partial combination with a deflector positioned above the central orifice, causes the water to fall back downward over the area to be sprinkled. In many prior upright sprinklers the deflector provides a somewhat concave undersurface relative to the sprinkler outlet orifice. In the past, such upright sprinkler deflectors have utilized smoothly curved undersurfaces and have also utilized planar undersurfaces with outer prongs disposed at an obtuse angle in efforts to obtain a downwardly directed spray of fluid.
Pendant sprinkler heads suffer from the disadvantage that rust or debris may tend to accumulate in an area 18 (FIG. 1) just above the top of the sprinkler head. Because these areas 18 are lower than the water supply pipe, any particles or debris in the water supply pipe will tend to eventually settle in these areas. If enough debris accumulates, it may interfere with the proper functioning of the sprinkler head, which, of course, is undesirable. Pendant sprinkler heads also suffer from the disadvantage that they cannot be used in cold areas where the temperature dips below the freezing level of the fire extinguishing fluid. After a single activation of the sprinkler system is such a cold area, the fluid would collect above the inactivated pendant sprinkler heads in the supply pipe and eventually freeze. The frozen pipes would prevent proper functioning of the sprinkler system.
Upright sprinkler heads do not suffer from the potential problem of debris accumulation because they are positioned above the water supply pipe. Whatever debris that may be present in the water supply pipe will settle on the bottom of the supply pipe where it will not interfere with the functioning of the sprinkler head. Moreover, upright sprinkler heads provide a generally faster response time than do pendant sprinkler heads because they can be positioned closer to the ceiling, due to the lack of an intervening supply pipe. Because the heat of a fire will rise to the ceiling and accumulate there, the closer the sprinkler head is to the ceiling, the faster it will be activated by the heat. Upright sprinkler heads, however, suffer from the disadvantage that the momentum of the water exiting the central orifice of the sprinkler head is vertically upward. The design of the sprinkler deflector and gravity must redirect the water flow toward the area to be protected since the fire will normally be below the sprinkler head. The momentum of the water, however, will therefore be in the "wrong" direction. The result of the upward momentum of the water in the past has been to produce a downwardly directed spray of water in the general area immediately below the upright sprinkler that lacks downward momentum except for that generated by gravity. Not only is this an inefficient use of the momentum of the water exiting the supply pipe, but it can lead to a diminished ability to extinguish a fire. Specifically, if the fire is large enough, the downward momentum of the water due to gravity may be insufficient to carry the water to the desired locations beneath the sprinkler. Instead, if the fire is large enough, the upward movement of the heat and air above the fire may be large enough to overcome the water's momentum and deflect the water, thereby preventing it from reaching certain areas of the fire. Such a result, of course, is undesirable.
The desirability of a sprinkler head that overcomes these and other disadvantages can therefore be seen.